1. Field of the Invention
The present invention relates to a flat panel display device. More particularly, the present invention relates to a method for fabricating an LCD device, in which a patterning process is performed without using photolithography. This simplifies the fabricating process while simultaneously improving the exactness of alignment. Thus, the thin film pattern for the flat panel display device is formed to be positioned correctly.
2. Discussion of the Related Art
The display technology industry has emphasized flat panel display devices as important visual information communication media. Display devices, such as devices including cathode ray tubes (CRTs) or Braun tubes, are losing popularity because they are inconveniently large and heavy.
Examples of flat panel display devices include liquid crystal display (LCD) devices, field emission display (FED) devices, plasma display panel (PDP) devices and electroluminescence (EL) displays. Most of these display devices are available to the ordinary consumer.
Recent breakthroughs in research and development have lead to improving mass production of these flat panel display devices. Accordingly, flat panel display devices have become viable replacements for CRTs in many applications.
Active matrix LCD devices provide excellent picture quality and consume little power. In active matrix LCD devices, a thin film transistor (“TFT”) is used to drive a liquid crystal cell. The improvements in the mass production of flat panel display devices have particularly lead to the rapid development of large and high-resolution active matrix type LCD devices.
An active matrix LCD device, as illustrated in FIG. 1, includes a color filter array substrate 22 and a TFT array substrate 23 bonded together with a liquid crystal layer 15 between them. The LCD device illustrated in FIG. 1 represents a part of the entire effective screen area.
The color filter array substrate 22 may include a color filter layer 13 and a common electrode 14 formed on the rear surface of an upper glass substrate 12. A polarizer 11 may be adhered to the front surface of the upper glass substrate 12. The color filter layer 13 may include red (R), green (G) and blue (B) color filters that transmit visible light in a specific wavelength band, thereby enabling color display. A black matrix (not shown) is formed between adjacent color filters in the color filter layer 13.
The TFT array substrate 23 includes data lines 19 and gate lines 18 that cross each other on the upper surface of a lower glass substrate 16. TFTs 20 are formed at the crossings of the data lines 19 with the gate lines 18. A pixel electrode 21 may be formed at a cell area between the data line 19 and the gate line 18 on the upper surface of the lower glass substrate 16. The TFT 20 switches a data transmission path between the data line 19 and the pixel electrode 21 in response to a scan signal from the gate line 18, thereby driving the pixel electrode 21. A polarizer 17 may be adhered to the rear surface of the TFT array substrate 23.
The liquid crystal layer 15 controls the amount of light transmitted through the TFT array substrate 23 by application of an electric field to the liquid crystal layer 15.
The polarizers 11 and 17 adhered to the color filter substrate 22 and the TFT substrate 23, respectively, polarize and transmit light in any direction. When the liquid crystal 15 is in a 90° twisted nematic (TN) mode, their polarizing directions perpendicularly cross each other.
An alignment film (not shown) may be formed on the liquid crystal layer 15 at surfaces opposite to the color filter substrate 22 and the TFT array substrate 23.
A related art process of fabricating the active matrix type LCD device includes a substrate cleaning process, a substrate patterning process, an alignment film forming/rubbing process, a substrate bonding/liquid crystal injecting process, a packaging process, an inspection process, a repair process and other suitable processes. The substrate cleaning process removes impurities that contaminate the substrate surface with a cleaning solution. The substrate patterning process includes a color filter substrate patterning process and a TFT array substrate patterning process. The alignment film forming/rubbing process coats an alignment film over each of the color filter substrate and the TFT array substrate, and rubs the alignment film with a rubbing cloth. The substrate bonding/liquid crystal injecting process bonds the color filter substrate with the TFT array substrate by using a sealant, injects liquid crystal and spacers through a liquid crystal injection hole, and then seals the liquid crystal injection hole. The packaging process connects a tape carrier package (TCP) to a pad part of the substrate. The TCP may be packaged with an integrated circuit (IC) such as a gate drive IC and a data drive IC. The drive IC may directly be mounted on the substrate by a chip-on-glass (COG) method and a tape automated bonding (TAB) method that uses the TCP. The inspection process may include an electrical inspection process that may be performed after forming the pixel electrode and the data lines and gate lines in the TFT array substrate. This inspection process also may include electrical inspection and macrography processes that may be performed after the substrate bonding/liquid crystal injecting process. If the outcome of the inspection process is a determination that the substrate is repairable, then restoration of the substrate is performed by a repair process. Also, the inspection process may determine that the substrate is sufficiently correct to go on to the next processing step. Substrates that are determined not to be repairable are disposed.
In fabricating most flat panel display devices including LCD devices, a thin film material deposited on the substrate may be patterned by a photolithography process. The photolithography process involves a series of photolithography steps such as photo-resist coating, mask aligning, exposure, development and cleaning. However, photolithography processes have several problems. For example, the time required to complete the photolithography process is long. Also, expensive equipment, such as exposure equipment, is required, and photo-resist materials and stripping solutions are wasted.